Fluid operated jacks

ABSTRACT

A jacking device for stressing or tensioning elongated reinforcing elements in concrete structures comprising an anchor homing jack and a stressing jack assembled in axial alignment, each jack having an annular cylinder surrounding an element to be stressed and an annular piston sliding in the cylinder, a tensioning member extending through both jacks and having means for engagement by the piston of the stressing jack and means associated with the piston of the homing jack to clamp the reinforcement elements after stressing to enable the jacks to be used for further stressing of the elements.

United States Patent [191 Persicke [111 3,811,653 [451 May 21, 1974FLUID OPERATED JACKS [75] Inventor: Gunter Persicke, Dartford, England[73] Assignee: Christiani and Nielson Limited,

London, England [22] Filed: July 31, 1970 [21] Appl. No.: 59,905

Related US. Application Data [63] Continuation-impart of Ser. No.739,l06, June 21,

I968, abandoned.

[30] Foreign Application Priority Data July 31, I969 Great Britain38551/69 [52] US. Cl 254/29 A [51] Int. Cl E2lb 19/00 [58] Field ofSearch 254/29 A [56] References Cited UNITED STATES PATENTS 2,763,4649/l956 Leonhardt 254/29 A 3,554,492 l/l97l Beghi 254/29 A PrimaryExaminer-Othell M. Simpson Attorney, Agent, or Firm.lohn P. Snyder [5 7]ABSTRACT A jacking device for stressing 0r tensioning elongatedreinforcing elements in concrete structures comprising an anchor homingjack and a stressing jack assembled in axial alignment, each jack havingan annular cylinder surrounding an'element to be stressed and an annularpiston sliding in the cylinder, a tensioning member extending throughboth jacks and having means for engagement by the piston of thestressing jack and means associated with the piston of the homing jackto clamp the reinforcement elements after stressing to enable the jacksto be used for further stressing of the elements. a

4 Claims, 8 Drawing Figures Pmmmmm 1914 3,811,653

SHEET 1 OF 6 Inventor I 24 5%? PER51CKE A ttomeys PATENTEDMAYZl 19743.811.653

' SHEET 2 or 6 In vvvv or GUNTE R PER sIcKE y MM A llll ney;

SHEET 3- BF 6 PATENTEDMAY 21 I974 v 1 Nil Inventor GUNTER PERSicKEPATENTEDMAYZT 1924 3,811,653

' saw u or e Inventor GWTER PER s i cm.

By} k Attorney PATENTEDMAYZI m4 sum 5 or 6 F/GZ WJENTEU MAY 2'! 1974SHEET 6 OF 6 FLUID OPERATED JACKS CROSS REFERENCE TO RELATEDAPPLICATIONS This application is a Continuation-in-part of our copendingapplication Ser. No. 739,106 filed June 21, 1968 now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to fluid actuated jacks primarily for use in prestressing aplurality of reinforcing cables or rods or like elongated elements in amould prior to pouring concrete into the moulds in making elongatedreinforced concrete structural elements such as piles or panels.

2. Description of the Prior Art In prestressing such reinforcingelements, the ends of the elements extend beyond the mould by asubstantial length, e.g., 4 feet, to give sufficient length on which thetensioning or stressing equipment can be engaged, and when thestructural element is completely set, the excess lengths of reinforcingelements are cut off which is a substantial waste of material. Moreoverwhen the reinforcing elements are laid in the mould or through bores inthe set concrete elements, an anchor is disposed on the end of the mouldor structural element through holes in which the ends of the reinforcedelements are passed, and a number of conical segments are disposed roundeach reinforcing element with their taper ends engaging in the anchorholes which are correspondingly tapered. When the reinforcing elementshave been fully stressed and the tensioning load is removed the segmentsmove into the holes and are wedged against the reinforcing elementsthereby firmly gripping them in tension. However before'the segmentsfully grip the reinforcing elements some v tension or stress in them islost due to the reinforcing elements running back into the moulds orbores. Also since the segments are located in the holes before thestressing is commenced, they tend during the stressing to move out ofthe holes and since the jack surrounds the reinforcing elements it isdifficult to prevent the segments falling out of the apparatus toreplace them if they do.

The main object of the present invention is to provide a fluid operatedjack in which these disadvantages are minimised or eliminated.

SUMMARY According to the prevent invention a fluid operated jack fortensioning or stressing reinforcement elements in concrete and likestructural members, comprises an anchor homing jack and a tensioning orstressing jack assembled in axial alignment, each jack being fluidoperated and formed of an annular piston sliding in an an nularcylinder, and a tensioning member having a portion at one end foranchoring to the reinforcing element or elements and at the other endmeans for engagement by the tensioning or stressing jack to be movedaxially thereby and impart a tensile force on each reinforcing element.

In a preferred construction for tensioning or stressing a plurality ofspaced reinforcing elements in a single constructional element theinterior of both jacks is longitudinallyhollow and the tensioning memberis located therein with its free end extending beyond the end of thetensioning or stressing jack and having an anchor member engaging theouter end of the extending member of the jack.

An anchor part preferably extends across the inner end of the hollowhoming jack, a number of axial holes are spaced round the anchor partthrough which the ends of the reinforcing elements are passed, and theanchoring portion of the tensioning member has axial holes therein inregister with the holes in the anchor part, said axial holes in theanchor part being axially tapered to receive anchoring segments disposedround the reinforcing elements.

The tensioning and homing jacks may be assembled with an axiallydisposed hollow stool member between them, the stool member and thecontiguous jack faces having interengaging profiles to locate the wholeassembly together in axial alignment when the reinforcing elements arebeing tensioned.

In another preferred embodiment the mould end of the block is providedwith a number of spaced axial bores spaced from the longitudinal axis ofthe device, a cylinder coaxial with said axis, a piston slidable axiallywithin said cylinder, and an element fast with the piston at the mouldend of the block and having bores therein in register with the bores inthe block.

The cylinder which is axially disposed in the block may extend out ofthe end of the block at the mould end thereof and the piston has aportion extending to the open end of the cylinder with the bored elementfast with the piston spanning the end of the block or a recess in theblock.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-section through ajack assembly;

FIGS. 2, 3 and 4 are respectively cross-sections on the lines IIII,IIl--III, and IVIV of FIG. 1 looking in the direction of the arrows;

FIG. 5 is a cross-section through an alternative construction of homingjack;

FIG. 6 is a plan view of the homing jack of FIG. 5,

FIG. 7 is a cross-section through another construction of the mouldengaging jack, and

. FIG. 8 is a cross-section similar to FIG. 7 showing an alternativeconstruction.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawings the samereferences are used to designate the same parts.

Referring to the drawings, FIGS. 1 to 4 show a fluid operated jack fortensioning or stressing reinforcement elements in concrete and likestructural elements which are not shown in the drawings. The jackcomprises a homing jack 1 and a tensioning or stressing jack 2 assembledin axial alignment, the jacks being fluid operated and including annularpistons 3 and 4 sliding in annular cylinders 5 and 6 respectively. Bothjacks are formed with a central bore in which is located a portion 8 atone end for anchoring to the reinforcing element or elements R and atthe other end 9 having means shown as a nut 10 for engagement with thejack 2 to be moved axially thereby and thus impart a tensile force oneach reinforcing element.

The jack 2 is constructed as described in our United Kingdom LettersPatent No. 992,405, while the jack 1 has a cylinder formed with a solidend, which may be welded on as in Application No. 17319/67, and isprovided at its open end with an annular flange 11 through which thetail of the piston 3 slides when the jack is operated. A fluid inlet 12has a bore extending into the head end of the cylinder and fluidpressure in the bore spreads the sealing ring 13 to engage the cylinderwall and thereby provide a fluid-tight seal between the piston and thecylinder. The cylinder 3 is formed by the external wall and an internalannular boss 14 which provides a hollow centre to the jack. The piston 3has an integral anchor part 15 extending across the hollow interiorpierced with a number of holes 16 for the purpose to be described.

The tensioning member 7 is located within the central bore of the twojacks and its free end 17 extends beyond the end of the jack 2, the nut10 being threaded onto the end as described. The other end 8 of themember 7 has a head 18 in which are formed tapered holes 19 in registerwith the holes in the anchor part 15.

As shown in the drawings which is a preferred construction the two jacksare separated by a stool member 20 the ends of which have a profileindicated at 21, 22 respectively corresponding to the. adjacent profilesof the two jacksso that in use the two jacks and the stool member aremaintained in axial alignment.

The stool member may be fabricated or formed from a single casting andis provided with windows 23 in its side to allow access to the member 7if required. This assists in the assembly of the device. round In 'use aplate 24 is disposed across the end of the member in which the elementsR are to be tensioned. This plate may form the end of a mould or may bea plate engaged with the concrete of the structural element. Thereinforcing elements R which are to be stressed may be for example rodsor cables and they are passed through the tapered holes 25 in the plate24. Tapering segments S are disposed around the reinforcing elementswith their ends engaging with the holes 25 and further segments S aredisposed roun the elements and extend into the apertures 19 in theportion 18.

When the jack 1 has been assembled with the reinforcing elements Rextending through the holes 16, the stool member 20 is placed inposition and the element 7 is then located inside the stool member withthe portion 8 inside the centre of the jack 1 with the reinforcingelements extending through the holes 19; the segments S are theninserted into the holes 19 around the reinforcing elements.

The jack 2 is then arranged in position and the nut 10 is screwed downonto the top end of the piston 4 of the jack 2. A pressure is applied tothe interior of the cylinder 6 through the piston 26; the piston 4 movesupwardly in the cylinder 6 and excess oil flows away from the other sideof the piston through the outlet 27. The pressure of the oil on bothsides of the piston 4 expands the sealing rings 28 and the packing ring29 to provide a fluid-tight seal. The movement of piston 4 in thecylinder 6 against the nut 10 lifts the tensioning member 7 which causesthe holes 19 in the element 8 to move over the segments 5' and jam thereinforcing elements R therein; the elements then begin to be tensioned.This action continues until either the reinforcing elements are extendedas far as possible, or the end of the reinforcing elements strike thetop end of the stool member 20.During this operation the anchor elementsS in the holes 25 have risen slightly to allow the reinforcing elementsto pass through them but they are prevented from coming out of the holes25 by the plate 15.

At this stage the pressure is maintained in the jack 2 and pressure isthen applied through the inlet 12 to the interior of the cylinder 5; thepiston 3 moves downwardly in the cylinder and the portion 15 is forceddownwardly towards the plate 24 thereby forcing the anchors S into theholes 25. This jams the reinforcing elements in the stressed position.It is now possible to dismantle the jack assembly and leave thereinforcing elements completely stressed and anchored within thestructural elements.

Referring to FIGS. 5 and 6, these show an alternative homing jack tothat shown in FIG. 1, the jack of FIGS. 5 and 6 comprising a bodyportion 26 having an upper flange 27 in which there are apertures 28.The bottom portion of the body 26 is downwardly and inwardly tapered andbeneath the holes 28 there are cut-a-way portions 29. The end of thebody 26 has a member 30 held by which pass through bores 31, the memberforming a closure for the bottom end of the cylinder 32 beneath thepiston 33. As in FIG. 1 the cylinder 32 is annular and its inner wall isformed by a hollow boss 34. This construction can be used where thereare a number of spaced reinforcing elements are to be stressed, theseelements being passed through the holes 28 and the cutaway portions 29.Alternatively, as stated a central tensioning member may be passedthrough the centre of the hollow cylinder 34.

FIG. 7 shows an alternative form of homing jack in which the lower end180 of the jack block is spaced from the stressing jack (not shown) bylongitudinal members 13a, of which a number are spaced round the block.

The block has a hollow central interior through which passes atensioning member 220 with a tensioning plate 210 fixed at its lowerend. The plate 210 has tapered bores 200 therein in which the free endsof the reinforcing elements (not shown) are anchored by taperedanchoring segments similar to those shown in FIG. 1, when the jackapplies an axial pull on the tensioning member away from the mould,tighten round the reinforcing elements to grip them.

Within the lower hollow block portion 180 are bores 118 parallel to theaxis of the central bore and in register with the bores 200 in the plate210. The portion 180 has a central axial clyinder within which slides apiston 119 with sealing rings 116 of suitable construction. The upperend of the cylinder has an enlarged portion into which is screwed a plug131 having sealing rings 132 round the cylinder surface. In itslower-most position the tensioning member 220 abuts at its bottom endagainst the plug 131. In its upper position the piston 119 abuts againstthe lower end of the plug 131 and a fluid inlet duct 133 supplied withfluid from a connector 134 leads into the small annular chamber 135surrounding the parts of the plug and the piston where they meet at 136so that pressure fluid introduced into the chamber 135 causes the piston119 to move down to its lowermost position.

The end of the cylinder has a narrower portion 137 and the piston isshaped with a shoulder 138 which in its lowermost position abuts theledge 139 between the wider and narrower parts of the cylinder.

Secured to the lower end of the piston and in a recess 140 in the block180, is an annular plate 141 having bores 142 therein in register withthe bores 118 in the block 180 and the bores 200 in the plate 210. Theplate 141 is secured to the piston by screws 143 and the thickness ofthe plate 141 is less than the depth of the recess 140 by a distanceequal to the height of the chamber 144 defined by the piston 119.

In operation the device is used to tension the reinforcing elementshaving their ends extending out of the mould or the end of the concreteelement through bores 136 in the plate 24 in which they are held byanchor elements (not shown) in the bores 136.

The device is assembled on the mould by threading the plate 24, theblock portion 180 and the plate 210 over the free ends of thereinforcement elements anchored by the taper anchored elements in theupper ends of the bores 136. The free ends of the elements pass rightout through the tapered portions of the top of the bores 200 in theplate 210 and anchor elements are placed in those tapered portions.

The stressing jack is then actuated to move the tensioning member 220axially away from the mould in the manner hereinbefore described so thatthe plate 210 applies a longitudinal pull on the elongated elementswhich are thus extended and stressed. During this stressing movement,the plate 141 is held upwardly by fluid pressure in space 144, and thispermits the anchor segments in the bores 136 to rise and release theelongated elements, but prevents them from passing out of the taperedportions 149 of the bores.

After stressing movement of the stressing jack, the homing jack in FIG.7 is actuated by causing fluid under pressure to pass into the chamber135 so that the piston l 19 is forced downwardly, thus moving the plate141 downwardly and jamming the anchor segments into the tapered portions149 of the bores 136 to grip the reinforcement elements in the extendedposition. The operation may then be repeated until the amount of stressrequired is applied to the elongated elements. The device may then bedismantled from the mould or concrete block being reinforced.

Referring to FIG. 8, this shows a similar homing jack to FIG. 7 but inthis embodiment the cylinder in the block portion 180 has an enlargedlower end 150 in which there is located a hollow securing ring 151 heldin position by threads 152. Sealing rings 153 are provided around thissecuring ring. The operation of this device is the same as describedwith reference to FIG. 7, the upper fluid chamber being locate above thepiston 119 and being supplied through the duct 133.

It will be seen that with a jack assembly such as described herein withreference to the drawings in accordance with the invention the sparelength of the reinforcing elements which extends beyond the structuralelements can be very short at the start of the tensioning operationwhich is a great saving on the existing forms of construction. Moreoverthe jack assembly automatically homes the segmental wedges round thereinforcing elements when the homing jack is operated so thatdismantling of the jack and leaving the reinforcing elements fullystressed in position is a simple operation.

The jack has a multiple use in that it can be used either as an ordinaryjack using in this case the jack 2, or

it can be used simply alone or with the stool member 7 for tensioning areinforcing element which passes right through the hollow portion of thecentre of the jack 2, or it can be used as described in the drawings fortensioning multi-cable or multi-rod cores through structural elements.

The jack is simple of construction, light in weight and can be operatedby inexpert operatives thereby greatly reducing the cost of tensioningsuch reinforcing ele- .ments.

I claim:

1. A stressing device for stressing elongate reinforcing elements inconcrete structures, comprising a base plate adapted to bear with oneface against the struc ture, a plurality of tapered bores in the baseplate through which the reinforcements may pass which bores widenoutwardly away from the said one face, two or more tapered anchoringsegments for disposition in each tapered bore, a homing jack in axialalignment with the base plate, said jack comprising an annular cylinderformed with an open end which bears against the base plate, a piston inthe cylinder movable under fluid pressure towards the base plate andopenings in the piston and in the cylinder in register with the bores inthe base plate for passage of the reinforcements therethrough, and astressing jack in axial alignment with the homing jack, the stressingjack comprising a cylinder block bearing on the homing jack, a centralbore in the cylinder block, an annular cylinder in the end of thecylinder block remote from the homing jack and an annular pistondisposed in the cylinder and movable under fluid pressure away from thehoming jack, and a tensioning member movable with the annular piston ofthe stressing jack and having means for gripping the reinforcements, sothat when the device is in use and the reinforcements are gripped by thetensioning member, movement of the piston in the stressing jack awayfrom the base plate causes the tensioning member to apply a tensioningforce to the reinforcements, and movement of the piston in the homingjack towards the base plate causes the piston to engage the taperedanchoring segments and drive said segments into the tapered bores in thebase plate to fix the position of the reinforcements with respect to thebase plate.

2. A stressing device according to claim 1, wherein the cylinder blockof the stressing jack bears on the homing jack through the intermediaryof a hollow cylindrical stool element disposed between the homing jackand the stressing jack and in axial alignment therewith.

3. A stressing device according to claim 2, wherein the contacting facesof the stressing jack, the stool element, and the homing jack areprovided with interengaging profiles.

4. A stressing device according to claim 1, wherein in the homing jack,the end of the cylinder is provided with an annular recess and the endof the piston extending out of the cylinder is provided with a platewhich spans the end of the cylinder and fits within said recess. =l

1. A stressing device for stressing elongate reinforcing elements inconcrete structures, comprising a base plate adapted to bear with oneface against the structure, a plurality of tapered bores in the baseplate through which the reinforcements may pass which bores widenoutwardly away from the said one face, two or more tapered anchoringsegments for disposition in each tapered bore, a homing jack in axialalignment with the base plate, said jack comprising an annular cylinderformed with an open end which bears against the base plate, a piston inthe cylinder movable under fluid pressure towards the base plate andopenings in the piston and in the cylinder in register with the bores inthe base plate for passage of the reinforcements therethrough, and astressing jack in axial alignment with the homing jack, the stressingjack comprising a cylinder block bearing on the homing jack, a centralbore in the cylinder block, an annular cylinder in the end of thecylinder block remote from the homing jack and an annular pistondisposed in the cylinder and movable under fluid pressure away from thehoming jack, and a tensioning member movable with the annular piston ofthe stressing jack and having means for gripping the reinforcements, sothat when the device is in use and the reinforcements are gripped by thetensioning member, movement of the piston in the stressing jack awayfrom the base plate causes the tensioning member to apply a tensioningforce to the reinforcements, and movement of the piston in the homingjack towards the base plate causes the piston to engage the taperedanchoring segments and drive said segments into the tapered bores in thebase plate to fix the position of the reinforcements with respect to thebase plate.
 2. A stressing device according to claim 1, wherein thecylinder block of the stressing jack bears on the homing jack throughthe intermediary of a hollow cylindrical stool element disposed betweenthe homing jack and the stressing jack and in axial alignment therewith.3. A stressing device according to claim 2, wherein the contacting facesof the stressing jack, the stool element, and the homing jack areprovided with interengaging profiles.
 4. A stressing device according toclaim 1, wherein in the homing jack, the end of the cylinder is providedwith an annular recess and the end of the piston extending out of thecylinder is provided with a plate which spans the end of the cylinderand fits within said recess.